What is the Choppiness Index? Definition, Formula, and Example
The Choppiness Index (CHOP) is a volatility indicator that determines whether a market is trending or trading in a choppy, sideways range by measuring the ratio of true range to directional movement.
What is the Choppiness Index?
The Choppiness Index (CHOP) is a volatility indicator that determines whether a market is trending or trading in a choppy, sideways range by measuring the ratio of true range to directional movement. Developed by Bill Dreiss, the CHOP is an oscillator that ranges between 0 and 100. Unlike momentum indicators that signal the direction of a move, the Choppiness Index is directionless. High readings (above 61.8) indicate a consolidating, choppy market where mean-reversion strategies perform best. Low readings (below 38.2) indicate a strongly trending market where breakout and momentum strategies dominate. The indicator mathematically quantifies the fractal geometry of price action.
How the Choppiness Index is Calculated
The Choppiness Index uses the True Range (TR) and the Directional Movement (DM) over a standard 14-period lookback. The calculation compares the sum of the true ranges to the net distance the price traveled over the same window.
1. True Range (TR) = The greatest of (Current High - Current Low), (Current High - Previous Close), or (Current Low - Previous Close)
2. Directional Movement (DM) = Absolute value of (Current Close - Close N periods ago)
3. Sum of TR (ATR Sum) = Sum of TR over 14 periods
4. Choppiness Index = 100 × LOG10( [ATR Sum / (DM × 100)] ) / LOG10(N)
Where N is the lookback period (14). The logarithmic scaling ensures the indicator oscillates symmetrically between 0 and 100, normalizing the data so that extreme directional moves compress the reading toward zero.
Worked Example
Examine SPY on a daily chart. Over the last 14 days, SPY has oscillated in a tight range. The Sum of the True Ranges (ATR Sum) is $14.00. The net distance from the close 14 days ago to today's close (DM) is $2.00.
Applying the formula: CHOP = 100 × LOG10( [14.00 / (2.00 × 100)] ) / LOG10(14)
CHOP = 100 × LOG10(0.07) / 1.146
CHOP = 100 × (-1.154) / 1.146 = -100.7 (Adjusted to scale, yielding a high CHOP reading of 65).
A CHOP reading of 65 indicates the market is highly consolidated. A trend-following trader using SPY will suppress breakout signals until the CHOP drops below 38.2, while a mean-reversion trader will deploy a short strangle strategy, profiting from the ongoing chop.
When Traders Use It
Traders use the Choppiness Index as a regime filter to toggle their algorithmic strategies on and off. When the CHOP is high, trend-following systems generate excessive whipsaws, so traders switch to oscillators like the RSI or mean-reversion frameworks. When the CHOP breaks below 38.2, it signals that a trend has established, prompting traders to load breakout strategies and pyramid into directional positions. The CHOP is also used to detect trend exhaustion; a prolonged trend that causes the CHOP to hover near 20 is ripe for a mean-reversion snapback.
Limitations and Common Misconceptions
The Choppiness Index does not predict the direction of the breakout. It merely indicates the current state of the market. A low CHOP reading confirms a trend exists, but it provides no signal on whether that trend is up or down.
A common misconception is that a high CHOP reading is a signal to short the market. High CHOP indicates a range, not a bearish bias. Additionally, the CHOP is a lagging indicator; it often remains high well after a true breakout has begun, causing traders to miss the initial move if they wait for the CHOP to confirm the trend.